JPH0571439A - Fuel injector - Google Patents

Abstract

PURPOSE:To downsize a fuel injector so as to improve the loading performance by specifying the ratio of engine rotating speed to pump rotating speed and increasing the rotating speed of a high pressure supply pump to reduce the number of crests of a cam and decrease the number of plungers. CONSTITUTION:A fuel injector of a diesel engine or the like includes a high pressure supply pump 6 having a plunger forced to reciprocate by a cam 72 driven by a crankshaft. The pump 6 force-feeds fuel flowing from a low pressure fuel passage in a pump chamber 21 into a common rail 4. A spill control solenoid valve 5 is interposed in a path communicating the pump chamber 21 with the low pressure fuel passage, whereby fuel force feed is started by opening the spill control solenoid valve 5 and high pressure fuel in the pump chamber 21 is forced to overflow to stop force feed by opening the valve according to the control of ECU 200. In this case, the ratio of engine rotating speed to pump rotating speed is set to less than 2, and the rotating speed of the high pressure supply pump 6 is increased so as to reduce the number of crests of a cam.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a pressure accumulating pipe (common rail) for use in an internal combustion engine such as a diesel engine.
Fuel injection device (high-voltage common rail system) having

[0002]

2. Description of the Related Art As an electronically controlled fuel injection device for an internal combustion engine, a common rail fuel injection device having excellent controllability has been developed. In this high-pressure common rail system, it is a technical problem to make the high-pressure supply pump for generating, maintaining, and controlling the common rail pressure corresponding to the injection pressure as compact as possible with a small drive torque. The applicant of this patent is JP-A-62-2581.
No. 60 proposes a fuel injection device using a variable discharge high-pressure supply pump of a system of controlling a pressure feeding stroke by a solenoid valve spill mechanism.

In this fuel injection device, as a high pressure supply pump, a pumping plunger (hereinafter referred to as a plunger) driven by a cam, a cylinder into which the plunger is inserted, and a pump chamber and a low pressure fuel passage communicate with each other at a predetermined time. It uses an intermittent reciprocating pump consisting of a feed hole. Further, in the high-pressure common rail system, the high-pressure supply pump supplies the fuel consumed by one injection to the common rail by the next injection timing. Therefore, unlike the conventional row-type injection pump, the discharge pressure of the pump is not used as it is for the fuel injection pressure, and a rapid rise of the discharge pressure is not required. Further, it is not necessary to match the number of cylinders n of the engine with the number of cylinders of the pump (the number of plungers).

[0004]

In order to make the fuel injection device compact, the number of cam peaks N in one cylinder of the pump is made plural, so that the number of cylinders of the pump can be reduced to n / N. Becomes However, increasing the number of cam peaks N is unavoidable because the base circle has to be large in order to prevent jumping of the cam due to design restrictions such as the cam peak profile being low speed, and the physique of the cam part is increased. The problem of increasing the size arises. An object of the present invention is to provide a fuel injection device that can simultaneously achieve a reduction in the number of cylinders of a pump and a compact cam portion.

[0005]

A fuel injection device of the present invention comprises a cam driven by a crankshaft of an internal combustion engine and a plunger reciprocally driven by the cam, and supplies fuel in a pump chamber flowing from a low pressure fuel passage. A high-pressure supply pump that pumps pressure into the common rail to generate a high predetermined pressure in the common rail is provided in a passage that connects the pump chamber and the low-pressure fuel passage.The fuel in the pump chamber overflows into the low-pressure fuel passage by opening the valve. The spill control solenoid valve to be caused to flow and the spill control solenoid valve during the discharge stroke of the high pressure supply pump are closed to start the pressure feeding, and are opened at a predetermined time during the pressure feeding stroke to open the high pressure fuel in the pump chamber. A discharge amount control means for causing the overflow to stop the pressure feeding, accumulates a fuel having a high predetermined pressure in a common rail, and injects this fuel into each cylinder of the internal combustion engine by an injection nozzle. The fuel injection system which is characterized in that a 2 less than the ratio of the engine speed and pump speed.

[0006]

According to the present invention, the ratio of the engine speed to the pump speed is less than 2, and the rotational speed of the high-pressure supply pump is increased to reduce the number N of cam peaks and to increase the plunger (pump). The number of cylinders is decreasing. As a result, the base circle of the cam can be made small and the number of plungers can be minimized, so that a fuel injection device having a small size and excellent mountability in the engine can be obtained. As described above, in the high-pressure common rail system, a low-speed cam profile is adopted because the discharge pressure of the pump does not directly become the fuel injection pressure and the pulsation of the common rail pressure is prevented. Therefore, the increase rate of the distance from the center of rotation of the cam surface is gradual, and the peak torque of the cam shaft required to drive the plunger of the pump can be set low. Therefore, the obstacles associated with the high speed operation of the pump are not a problem.

[0007]

An embodiment of the present invention will be described with reference to the drawings. FIG. 1 shows a high-pressure common rail system 100 applied to a 4-cycle, 6-cylinder engine 1. The six injectors 2 mounted on each cylinder of the engine 1 are connected to the common rail 4 via the injection control solenoid valves 3, respectively.
A variable discharge high pressure supply pump 6 having a spill control solenoid valve 5 attached thereto is connected to the common rail 4, and this pump 6
Are driven by the pump cam type drive mechanism 7 (FIG. 2). The injection control solenoid valve 3 and the spill control solenoid valve 5 are controlled according to operating conditions by an electronic control unit (ECU) 200 that inputs information from various sensors mounted on the engine 1 to control the fuel injection amount. And a pump discharge amount control means.

That is, the high voltage common rail system 10
To the ECU 200 that controls 0, the engine speed sensor 11, the load sensor 12, and the pressure sensor 13 that detects the common rail pressure are input with information about the speed and the load and the common rail pressure. The ECU 200 performs the negative feedback control of the common pressure while controlling the injection control solenoid valve 3 so that the optimum injection timing and injection amount (= injection time) are determined according to the engine state determined from these signals. And a control signal to the spill control solenoid valve 5 to control the common rail pressure to the optimum injection pressure.

The common rail pressure is controlled as shown in the time chart of FIG. For example, of fuel in the common rail 4 accumulated at a pressure of 100 MPa, each time a control pulse to the injection control solenoid valve 3 is generated, a certain amount of diagonally shaded (injection amount and hydraulic servo control of nozzles, etc. (Equivalent to the fuel consumed) is consumed. To compensate for this, the high-pressure supply pump 6 intermittently discharges only the necessary amount (hatched portion) corresponding to the consumption amount into the common rail 4 in order to always maintain the common rail pressure at a constant 100 MPa level. Since this required amount changes depending on the injection amount and the number of revolutions, the spill control solenoid valve 5 operates to adjust the discharge amount of the high-pressure supply pump 6 once. In order to supply, maintain and control such high pressure, one operating cycle of the injection device,
That is, it is advantageous that the fuel is replenished for each injection in synchronization with each cycle.
For this, an intermittent reciprocating jerk pump that pumps fuel for the number of engine combustions is used.

Next, the high pressure supply pump 6 and the pump drive mechanism 7 will be described with reference to FIG. Reference numeral 60 denotes a pump housing, and a cam chamber 70 of the pump drive mechanism 7 is formed at the lower end thereof. A cylinder 61 is provided in the pump housing 60.
A plunger 62 is reciprocally and slidably fitted in the cylinder 61.
A pump chamber 21 is formed by the upper end surface of the plunger 62 and the inner peripheral surface of the cylinder 61. The cylinder 61 has a feed hole 22 as a communication passage communicating with the pump chamber 21 and an upper portion of the feed hole 22 in the drawing. Only the discharge hole 23 communicating with the pump chamber 21 at the position is formed. The feed hole 22 communicates with a fuel pool 24 formed between the cylinder 61 and the pump housing 60, and the fuel pool 24 is connected to the fuel pool 24 via an introduction pipe 25 by a low pressure supply pump 81 (FIGS. 1 and 2). Low pressure fuel is supplied. A check valve 26 is attached to the cylinder 61, and the check valve 26 communicates with the pump chamber 21 via the discharge hole 23. The fuel pressurized in the pump chamber 21 pushes the valve body 27 of the check valve 26 open against the urging force of the return spring 28, and the high pressure fuel pressurized by this pushes in the common rail 4 through the discharge port body 29. Pumped to.

The lower end of the plunger 62 is connected to a valve seat 63, and the valve seat 63 is connected to the plunger spring 6
It is pressed against the follower 65 by 4. The follower 65 has a cam roller 66.
Reference numeral 6 is in sliding contact with a cam 72 of the pump drive mechanism 7, which will be described later. Therefore, when the cam 72 rotates due to the rotation of the cam shaft 71, the plunger 62 is reciprocally driven through the cam roller 66 and the valve seat 63. The reciprocating stroke of the plunger 62 is determined by the height difference of the cam 72. Therefore, when the plunger 62 reciprocates in the cylinder 61, the outer peripheral surface of the plunger 62 opens and closes the feed hole 22, and when the outer peripheral surface of the plunger 62 does not block the feed hole 22, the feed hole 22 is opened. Fuel on the low pressure side is supplied to the pump chamber 21 via the low pressure side.

A spill control solenoid valve 5 which constitutes a discharge amount control means together with the ECU 200 is screwed and fixed to the cylinder 61 at a position facing the upper end surface of the plunger 62. In this spill control solenoid valve 5, the outer peripheral surface of the plunger 62 closes the feed hole 22, and then the valve body 51 is seated on the seat portion 52 by pressurizing the plunger 62 by energizing at a predetermined timing. It is a pre-stroke control type solenoid valve that sets the start time. The discharge amount to the common rail 4 can be changed by controlling the timing of energizing the spill control solenoid valve 5.
The low pressure passage 54, which communicates with the pump chamber 21 via the valve port 53 when the valve is open, communicates with the fuel reservoir 24 via the gallery 55 and the passage 56.

The pump drive mechanism 7 is connected to the crankshaft of the engine through a triple speed increasing mechanism (neither is shown), and serves as a pump drive shaft that rotates at a speed of 3/2 of the engine speed. The camshaft 71 is provided. Figure 2
As shown in FIG. 5, a cam 72 is formed on the cam shaft 71, and the cam 72 has a two-stroke ascending stroke per one rotation of the cam shaft 71, that is, a double-hill cam form. The cam 72 and the rotary disks 73 and 74 are shown rotated 90 degrees. As shown in FIG. 4, the cam surface profile of the cam 72 is a low-speed drive profile in which the increase rate of the radius from the rotation center is smaller than that in the case of the row fuel injection pump (shown by the broken line). For this reason, the peak value of the torque required to push up the plunger 62 is small, and even if the cam is rotated at high speed, problems such as jumping of the plunger 62 are unlikely to occur.

In order to control the spill control solenoid valve 5, as shown in FIG. 2, a rotating disk 73 having a number of projections corresponding to the number of engine cylinders (six in this embodiment) is coaxial with the camshaft 71. The cam angle sensor 14, which is a known electromagnetic pickup, is mounted facing the protrusion. A signal is sent to the ECU 200 each time the protrusion passes near the cam angle sensor 14. The mounting phase of the rotary disk 73 is determined so as to approach the cam angle sensor 14 at the rotational phase of the cam 72 near each bottom dead center. Further, a disc 74 having only one protrusion is coaxially attached to the camshaft 71, and the cylinder discrimination sensor 1
5 are arranged. Therefore, the ECU 200 receives one signal per one rotation of the pump from the cylinder discrimination sensor 15. The ECU 200 discriminates and obtains the bottom dead center signal of the pump specific cylinder from the signals of the cylinder discrimination sensor 15 and the cam angle sensor 14.

The plunger 62, which is reciprocated with the rotation of the camshaft 71, is lowered when the plunger 6 is lowered.
2 opens the feed hole 22, and this feed hole 2
When the fuel is introduced into the pump chamber 21 via 2 and the outer peripheral surface of the plunger 62 closes the feed hole 22 when rising, the plunger 62 tries to pressurize the fuel in the pump chamber 21. However, since the spill control solenoid valve 5 is not energized at this time, the valve body 51 is open,
The fuel in the pump chamber 21 overflows through the valve port 53, the low pressure passage 54, the gallery 55, and the passage 56 in order. When a control pulse is sent to the spill control solenoid valve 5 while the fuel in the pump chamber 21 is overflowing, the valve body 51 is seated on the seat portion 52 and the valve port 53 is closed. Therefore the plunger 62
When the fuel pressurization in the pump chamber 21 is started by and the fuel pressure in the pump chamber 21 overcomes the urging force of the spring 28 provided behind the check valve 26, the fuel pumped through the discharge hole 23 is released. The body 27 is pushed open and discharged into the common rail 4 through the discharge port body 29.

Next, the operation of the high-voltage common rail system 100 having the above structure will be described with reference to FIG. FIG. 5 shows the operation of the high-pressure supply pump 6 for three revolutions (two revolutions of the engine).
It is a time chart shown over. The signal of the cylinder discrimination sensor 15 of FIG. 1 in FIG. 1A and the cam angle sensor 14 in FIG.
The ECU 200 detects the specific cam phase of the pump specific cylinder (for example, in the vicinity of the bottom dead center) based on this signal. (C) shows the lift of the cam 72, and in the structure of the double ridged cam of FIG. 2, during three rotations of the cam shaft 71, the pressure feeding corresponding to the number of engine cylinders is performed six times. With respect to the cam lift, the alternate long and short dash line corresponds to the pressure feed start timing, and the alternate long and short dash line corresponds to the spill timing from the spill control solenoid valve 5. Only the portion of the high-pressure supply pump 6 between the pressure feed strokes is discharged into the common rail 4.

(D) shows a control signal to the spill control solenoid valve 5 of FIG. In the present embodiment, the ECU 200 energizes (closes the valve) in synchronization with the cam angle signal corresponding to the spill control solenoid valve 5 in the pressure feeding stroke, and terminates energization after a time T corresponding to the required discharge amount of the system. (Open the valve). The pressure feeding stroke of the high-pressure supply pump 6 starts at the timing of and ends by the spill from the spill control solenoid valve 5. Therefore, the fuel in the hatched portion in FIG. 5 is discharged into the common rail 4. Here, since the time T is increased / decreased according to the load, the rotation speed, or the signal from the pressure sensor, the pump discharge amount to the common rail 4 can be controlled.

The ratio of engine speed to pump speed is
An integer ratio of less than 2 is desirable. In addition to the above-described embodiment, for example, for a 6-cylinder engine, a pump 1 cylinder (1 plunger) with 3 hill cams and a rotation speed ratio of 1: 1 or a 4 hill cam with 1 plunger and a rotation speed ratio of 4: For a 3- or 8-cylinder engine, a four-cylinder cam has one plunger and a rotational speed ratio of 1: 1, or a three-cylinder cam has one plunger and a rotational speed ratio of 3: 4. As a result, by changing the gear ratio of the speed increasing mechanism between the crankshaft and the camshaft 71, the high pressure supply pump 6 can change the control system with one model and handle any engine 1. It is also possible to replenish the fuel lost from the common rail 4 by one injection with the injector 2 by discharging the pump a plurality of times. As a result, the discharge amount per pump is reduced, the drive torque can be further reduced, and the pulsation of the internal pressure of the common rail 4 can be reduced.

[Brief description of drawings]

FIG. 1 is a schematic view of a fuel injection device of the present invention.

FIG. 2 is a schematic diagram of a high voltage common rail system.

FIG. 3 is a time chart for explaining the operation of the apparatus of FIG.

FIG. 4 is a sectional view of a spill control solenoid valve.

5 is a time chart for explaining the operation of the apparatus of FIG.

[Explanation of symbols]

 1 engine 2 injector 3 injection control solenoid valve 4 common rail 5 spill control solenoid valve 6 high-pressure supply pump 7 pump drive mechanism 71 camshaft 72 cam 100 common rail system 200 electronic control unit (ECU)

Claims (1)

[Claims] 1. A cam driven by a crankshaft of an internal combustion engine, and a plunger reciprocally driven by the cam,
A high-pressure supply pump that pumps the fuel in the pump chamber flowing from the low-pressure fuel passage into the common rail to generate a high predetermined pressure in the common rail, and a passage that connects the pump chamber and the low-pressure fuel passage to each other. Spill control solenoid valve that causes the fuel to overflow into the low-pressure fuel passage by opening the valve, and the spill control solenoid valve that closes the spill control solenoid valve during the discharge stroke of the high-pressure supply pump to start the pressure feed, and at a predetermined time during the pressure feed stroke. A discharge amount control means for opening the valve to cause the high pressure fuel in the pump chamber to overflow to stop the pressure feeding, accumulate fuel of a high predetermined pressure in a common rail, and inject this fuel into each of internal combustion engines by an injection nozzle. A fuel injection device for injecting fuel into a cylinder, wherein a ratio of an engine speed and a pump speed is less than 2.